All of these situations will cause instant heartbreak, along with a certain sense of panic. What do you do now? I'll try to answer some of the situations that may occur, keeping in mind that I don't know all the answers.
Will someone come to my home and take away the body?
If you are have a mobile veterinary clinic in your area, they may be able to accomodate your needs. Animal control services will also pick up dead owned animals, usually for a charge. Dead pets are not considered an emergency, however, so at night or on weekends or holidays, they may refuse to respond.
If there is a delay, what do I do with my cat's body?
You may wish to clean the body up a bit first. Just like people, cats' organs will relax upon death, and fecal matter and urine may be expelled. Then, depending on the length of the delay, you may be able to just wrap the body carefully in towels and place it in an appropriately sized box. If you have to wait more than two hours, or in hot weather, wrap the remains thoroughly in plastic wrap, place it in a large plastic bag, tie it closed tightly, and place it in a styrofoam ice chest with ice packed all around. (Make sure there is a drainage hole in the bottom for draining water.) I know these details are painful to think about, and even more painful to perform, but try to remember that your cat's essence is no longer in his body. Be strong, and remember that we are capable of heroic acts we never thought we could perform, when called upon to do so. Your careful, respectful handling of your beloved cat's remains will serve as a testament to your love.
When It's All Over
When you have handled all the final details, the enormity of your loss may hit you immediately, or you may find yourself feeling numb and unable to cry. Grieving any loss is a long process, and you will never feel fully "recovered." But by understanding and recognizing the progressive stages of grief, the day will come, sooner or later, when you will be able to look back on your life together with love, and smiles instead of tears.